Natural fiber composites manufacturing process

As an extension to the considerable amount of research undertaken on processing and properties of natural filler composites, in this last decade, a number of researchers have explored the concept of namral filler-reinforced PLA composites. An outstanding one is the project FAlR-CT-98-3919 (New ftmctional biopolymer-natural fiber composites from agriculture resources) by European Union, in which one of the key objectives was to manufacture demonstration parts on a pre-competitive level with the automotive industry as the main potential market. Within this project, Lanzillotta et al. [21] prepared biocomposites with flax fibers and PLA as the biopolymer matrix. The research focused on the idea of converting biocomposites into products for real automotive applications. 

Three-dimensional glass fiber, as shown as 5 of Figure 52, can be used for batch and continuous processes (23, 24). This foamed composite is proposed for use in cryogenic insulation, such as liquid natural-gas tank insulation. However, its manufacturing process seems to be very complex and production costs would be high. 

Customer preferences for recycled products have encouraged a more efficient use of wood and natural fibers. One potential approach to preserve wood and use natural fibers is the development of commodity-engineered composites that blend wood and natural fibers with other materials, such as plastic. The idea of combining wood and plastic is to produce a product with performance characteristics that combine the positive attributes of both materials. Wood and other natural fibers have been used as fillers and/or reinforcement to improve the mechanical properties of a variety of products. The combination of wood and plastic creates the ability to develop diverse products using many different manufacturing processes. 

Natural fibers can be classified as seed fibers (such as cotton), bast fibers (like flax, hemp, jute, kenaf, ramie), hard fibers (like sisal), fi-uit fibers (like coir), and wood fibers. The chemical composition and dimensions of some common agro-fibers are presented in Table 5.21. The origin of wood fibers can be sawmill chips, sawdust, wood flour or powder, cutter shavings, pulp or wood residues. As binders for these fibers, both thermosetting (like phenolic, epoxy, polyester) resins and thermosetting matrices [such as polyethylene (LDPE, HDPE), polypropylene (PP), poly(vinyl chloride) (PVC), polystyrene (PS)j can be used. Thermoplastic composites are, however, less expensive to process than thermosetting composites, in addition to their ability to be manufactured into complex shapes. 

The demand for better fuel efficiency based on the strict governmental regulations on safety and emission has led to the wide application of composites and plastics in the automotive industry in the place of the traditionally used steels [32]. Thermoplastic materials reinforced with natural fibers have reported to have excellent mechanical properties, recycling properties, etc. [33-36]. Several natural and biorenewable fibers such as wheat, isora, soybean, kenaf, straw, jute, and sisal are used in the fiber/plastic composite industry, and the use of namral fibers as reinforcements for composite has attracted many industries [37, 38]. Compared to polymer resin, polymer biocomposites that are reinforced with natural fibers have many applications due to its ease of processing, comparatively lower cost, and excellent mechanical properties [39]. For more than a decade, European car manufacturers and suppliers have been using natural fiber-based composites with thermoplastic and thermoset matrices. These biocomposites and bionanocomposites... 

A thermoplastic polymer composition reinforced with fibers such as cellulose or other fillers, particularly from natural sources, and a process for manufacturing the composition has been described (26). The polymer is extruded with a salt which reduces the melting point and pelletized. The pellets are then extruded again with the filler. The composition with the filler can then be melted at the reduced melting temperature to manufacture an article. 

Abstract A wide variety of natural fibers can be applied as reinforcement or fillers in composites. Bast fibers, such as fiax and hemp, have a long history of cultivation and use. They are characterized by low weight and excellent range of mechanical properties. The properties of bast fibers are influenced by conditions of cultivation, retting, and processing. Pretreatment and surface modification of bast fibers is conducted for optimization of the interfacial characteristics between fiber and matrix as well as improvement of their mechanical properties. Application of bast fibers as reinforcement to replace the glass fibers to composite manufacture brings positive environmental benefits. 

A study on hybrid composites of sisal fiber with other natural fibers or synthetic fiber is needed to achieve optimum benefit for broader applications. Sisal fiber/ matrix interface and relationship between interface and bulk composites need to be studied in detail for a better understanding leading to the development of a unique process for better bonding between fiber and matrix and compatibility with a wider range of other materials/components. Further R D, new initiatives, and innovation are needed to develop a unique mechanism for the manufacture of environmental... 

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